39,384 research outputs found
An Efficient Algorithm for Mining Frequent Sequence with Constraint Programming
The main advantage of Constraint Programming (CP) approaches for sequential
pattern mining (SPM) is their modularity, which includes the ability to add new
constraints (regular expressions, length restrictions, etc). The current best
CP approach for SPM uses a global constraint (module) that computes the
projected database and enforces the minimum frequency; it does this with a
filtering algorithm similar to the PrefixSpan method. However, the resulting
system is not as scalable as some of the most advanced mining systems like
Zaki's cSPADE. We show how, using techniques from both data mining and CP, one
can use a generic constraint solver and yet outperform existing specialized
systems. This is mainly due to two improvements in the module that computes the
projected frequencies: first, computing the projected database can be sped up
by pre-computing the positions at which an symbol can become unsupported by a
sequence, thereby avoiding to scan the full sequence each time; and second by
taking inspiration from the trailing used in CP solvers to devise a
backtracking-aware data structure that allows fast incremental storing and
restoring of the projected database. Detailed experiments show how this
approach outperforms existing CP as well as specialized systems for SPM, and
that the gain in efficiency translates directly into increased efficiency for
other settings such as mining with regular expressions.Comment: frequent sequence mining, constraint programmin
Pinworms of the red howler monkey (Alouatta seniculus) in Colombia. Gathering the pieces of the pinworm-primate puzzle
Pinworms of primates are believed to be highly host specific parasites, forming co-evolutionary associations with their hosts. In order to assess the strength and reach of such evolutionary links, we need to have a broad understanding of the pinworm diversity associated with primates. Here, we employed an integrative taxonomic approach to assess pinworm diversity in red howler monkeys in Colombia. Molecular and morphological evidence validate the presence of at least four different species of Trypanoxyuris occurring in red howler monkeys: T. minutus, a widely distributed species, and three new species, T. seunimiii n. sp., T. kemuimae n. sp. and T. kotudoi n. sp. The mitochondrial COI gene and the 28S ribosomal gene were used for phylogenetic assessments through Bayesian inference. The three new species were morphologically distinct and formed reciprocally monophyletic lineages. Further molecular lineage subdivision in T. minutus and T. kotudoi n. sp. without morphological correspondence, suggests the potential scenario for the existence of cryptic species. Phylogenetic relationships imply that the different species of Trypanoxyuris occurring in each howler monkey species were acquired through independent colonization events. On-going efforts to uncover pinworm diversity will allow us to test the degree of host specificity and the co-phylogenetic hypothesis, as well as to further unravel the primate-pinworm evolutionary history puzzle
The jet of Markarian 501 from millions of Schwarzschild radii down to a few hundreds
Aims: The TeV BL Lac object Markarian 501 is a complex, core dominated radio
source, with a one sided, twisting jet on parsec scales. In the present work,
we attempt to extend our understanding of the source physics to regions of the
radio jet which have not been accessed before.
Methods: We present new observations of Mrk 501 at 1.4 and 86 GHz. The 1.4
GHz data were obtained using the Very Large Array (VLA) and High Sensitivity
Array (HSA) in November 2004, in full polarization, with a final r.m.s. noise
of 25 microJy/beam in the HSA total intensity image; the 86 GHz observations
were performed in October 2005 with the Global Millimeter VLBI Array (GMVA),
providing an angular resolution as good as 110 x 40 microarcseconds.
Results: The sensitivity and resolution provided by the HSA make it possible
to detect the jet up to ~700 milliarcseconds (corresponding to a projected
linear size of ~500 pc) from its base, while the superior resolution of the 86
GHz GMVA observations probes the innermost regions of the jet down to ~200
Schwarzschild radii. The brightness temperature at the jet base is in excess of
6e10 K. We find evidence of limb brightening on physical scales from <1 pc to
~40 pc. Polarization images and fits to the trend of jet width and brightness
vs. distance from the core reveal a magnetic field parallel to the jet axis.Comment: 10 pages, accepted by A&
Martian impact crater ejecta morphologies as indicators of the distribution of subsurface volatiles
Fresh Martian impact craters display a variety of ejecta blanket morphologies. The fluidized appearance of most fresh ejecta types is commonly ascribed to heating and
vaporization of subsurface volatiles during crater formation. We have conducted a study of the distribution of the three dominant fluidized ejecta morphologies (single layer ejecta (SLE), double layer ejecta (DLE), and multiple layer ejecta (MLE)) within the ±60°
latitude zone on Mars. We have subdivided this region into 5° x 5° latitude-longitude boxes and have computed the following for each box: (1) percentage of craters showing
any ejecta morphology as a function of total number of craters, (2) percentage of SLE craters as a function of craters with an ejecta morphology, (3) percentage of DLE craters as a function of craters with an ejecta morphology, and (4) percentage of MLE craters as a
function of craters with an ejecta morphology. We confirm previous reports that the SLE morphology is the most common ejecta type within the study area, constituting >70% of all ejecta morphologies over most of the study area. The DLE and MLE morphologies are much less common, but these morphologies are concentrated in localized regions of the planet. Using these results, we discuss how subsurface volatile reservoirs may be
distributed across the planet. The regional variations found in this study generally correlate with the proposed locations of near-surface H2O reservoirs detected by Mars
Odyssey
Fatal attraction: identifying mobile devices through electromagnetic emissions
Smartphones are increasingly augmented with sensors for a variety of purposes. In this paper, we show how magnetic field emissions can be used to fingerprint smartphones. Previous work on identification rely on specific characteristics that vary with the settings and components available on a device. This limits the number of devices on which one approach is effective. By contrast, all electronic devices emit a magnetic field which is accessible either through the API or measured through an external device.
We conducted an in-the-wild study over four months and collected mobile sensor data from 175 devices. In our experiments we observed that the electromagnetic field measured by the magnetometer identifies devices with an accuracy of 98.9%. Furthermore, we show that even if the sensor was removed from the device or access to it was discontinued, identification would still be possible from a secondary device in close proximity to the target. Our findings suggest that the magnetic field emitted by smartphones is unique and fingerprinting devices based on this feature can be performed without the knowledge or cooperation of users
Grafting melons onto potential cucumis spp. rootstocks
CucumĂs
melo
is
an
economically
importar]t
crop.
Its
culture
is
hampered
by
differen
t
types
of
soil
stresses.
Grafting
melons
onto
different
resistant
cucurbits
belonging
to
the
genera,
CucurbĂta,
LagenarĂa,
Luffa,
etc.
have
been
successfully
used
to
avoid
these
problems.
However,
me
Ion
quality
has
been
nega.tively
modified
as
a
consequence
of
grafting.
In
general,
variation
in
fruit
shape,
seed
cavity
and
sugar
content
have
been
observed.
The
use
of
rootstocks
more
genetically
c\oser
to
the
melon
scions
could
be
useful
to
obtain
fru
i
ts
with
better
quality
from
melon
grafted
plantsPostprint (published version
Martian impact crater ejecta morphologies as indicators of the distribution of subsurface volatiles
[1] Fresh Martian impact craters display a variety of ejecta blanket morphologies. The fluidized appearance of most fresh ejecta types is commonly ascribed to heating and vaporization of subsurface volatiles during crater formation. We have conducted a study of the distribution of the three dominant fluidized ejecta morphologies ( single layer ejecta (SLE), double layer ejecta (DLE), and multiple layer ejecta (MLE)) within the +/- 60degrees latitude zone on Mars. We have subdivided this region into 5degrees x 5degrees latitude-longitude boxes and have computed the following for each box: (1) percentage of craters showing any ejecta morphology as a function of total number of craters, (2) percentage of SLE craters as a function of craters with an ejecta morphology, (3) percentage of DLE craters as a function of craters with an ejecta morphology, and (4) percentage of MLE craters as a function of craters with an ejecta morphology. We confirm previous reports that the SLE morphology is the most common ejecta type within the study area, constituting \u3e 70% of all ejecta morphologies over most of the study area. The DLE and MLE morphologies are much less common, but these morphologies are concentrated in localized regions of the planet. Using these results, we discuss how subsurface volatile reservoirs may be distributed across the planet. The regional variations found in this study generally correlate with the proposed locations of near-surface H2O reservoirs detected by Mars Odyssey
Exact Matrix Product States for Quantum Hall Wave Functions
We show that the model wave functions used to describe the fractional quantum
Hall effect have exact representations as matrix product states (MPS). These
MPS can be implemented numerically in the orbital basis of both finite and
infinite cylinders, which provides an efficient way of calculating arbitrary
observables. We extend this approach to the charged excitations and numerically
compute their Berry phases. Finally, we present an algorithm for numerically
computing the real-space entanglement spectrum starting from an arbitrary
orbital basis MPS, which allows us to study the scaling properties of the
real-space entanglement spectra on infinite cylinders. The real-space
entanglement spectrum obeys a scaling form dictated by the edge conformal field
theory, allowing us to accurately extract the two entanglement velocities of
the Moore-Read state. In contrast, the orbital space spectrum is observed to
scale according to a complex set of power laws that rule out a similar
collapse.Comment: 10 pages and Appendix, v3 published versio
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